Physicochemical and structural information

Stmcture. related to the. spatial arrangement of atoms, and groups of atoms or molecules. This ranges from long-range order, characteri.stic of crystalline compounds, and established by conventional diffraction techniques, to friction-induced short-range order (local order) established by more specialized techniques. as detailed hereunder. 

XAS requires synchrotron radiation and a relatively large amount of material but no vacuum condition. On the other hand, EELS can be performed directly using an electron spectrometer fitted to a scanning transmission electron microscope (STEM). Here, the main advantage is the high spatial resolution attainable. (The incident electron beam can be as. small as I nm in diameter.) EELS can also be coupled with conventional transmission electron microscope (TEM) facilities and particularly high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS). 

The analysis of friction interfaces in motion is feasible in vivo configuration, see Section 2.2) due to the high transparency of the matter to X-rays (Fig. 5c). Martin et al. have developed a tribometer which can be coupled to both X-ray absorption spectroscopy (XAS) and Raman spectroscopy (Fig. 6) [14], illustrating the desirable coupling of the time-scale criterion mentioned above with the information from the analysis. For this purpose, X-ray-lransparenI sup- 

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